Ringing user inserting method

A method for insertion operation to the user in ringing state includes calling a called user by a calling user, linking them for talking, another calling to the calling user by a higher-priority user, insertion operation by telephone operator, invoking the calling processes for said calling user and telephone operator, judging if the calling user is in ringing state, if not connecting the meetingcircuit to the calling process of called user in three-party talking state, informing the calling user of the talking requirement from higher-priority user, disconnecting the called user, and connecting the calling user to the high-priority user.